It is currently Mon Mar 16, 2020 10:53 am

All times are UTC - 7 hours



Post new topic Reply to topic  [ 21 posts ]  Go to page 1, 2  Next
Go to page 1, 2  Next
Author Message
Post subject: Deluxe Reverb Vibrato PLate Voltage High
Posted: Mon Nov 23, 2015 7:18 pm
Offline
Hobbyist
Hobbyist

Joined: Sun Oct 07, 2012 6:48 pm
Posts: 74
Hi There

I have a pretty stock Blackface 1966 Deluxe Reverb

I was checking the plate voltages and I noticed that the plate on V5 (Pin 1) is really high. A few other spots are a bit high or Low..but nothing as much as the 390 VDC where it should be 270VDC

http://www.thevintagesound.com/ffg/sche ... _schem.gif

I'd like to get the amp working at spec. The filter caps have been done with Sprague Atoms, the tubes are new.
Bias King Reading 20Ma both tubes

I wrote in the readings Im getting on the Schematic, any thoughts?

Image

Image[/URL]

Image[/URL]

Image[/URL]


Top
Profile
Fender Play Winter Sale 2020
Post subject: Re: Deluxe Reverb Vibrato PLate Voltage High
Posted: Mon Nov 23, 2015 11:24 pm
Offline
Rock Icon
Rock Icon
User avatar

Joined: Wed Mar 31, 2010 12:48 am
Posts: 26416
Location: Tombstone Territory
Are you using a 100/100 bias cap?

I've always thought those values were to high compared to the original specs as per the schematic.

BTW, the date stamped on your chassis indicates the amp was assembled in the 18th week of 1967.

Arjay

_________________
"Here's why reliability is job one: A great sounding amp that breaks down goes from being a favorite piece of gear to a useless piece of crap in less time than it takes to read this sentence." -- BRUCE ZINKY


Top
Profile
Post subject: Re: Deluxe Reverb Vibrato PLate Voltage High
Posted: Mon Nov 23, 2015 11:27 pm
Offline
Rock Star
Rock Star
User avatar

Joined: Sat Jul 03, 2010 2:18 pm
Posts: 6544
Which side of the 220k-ohm anode loading resistor are you reading the VDC? The voltage supplying pin 1 of the Vibrato tube (V5)? See the layout. If you are the blue dot side... voltage = about 410VDC. Red dot side = 250VDC.

BTW... did you have the vibrato and reverb turned on, when measuring the voltage? If they were off, the plate voltages may read a bit higher.

Noticed that the global feedback resistor was changed to 1k-okm (brown-black-red) by green dot. Wonder why this was done? The 820 ohm resistor is classic blackface. The difference is minimal and won't make that much difference. Just wondered why this was done?



Image


Last edited by BMW2002Ti on Mon Nov 23, 2015 11:40 pm, edited 4 times in total.

Top
Profile
Post subject: Re: Deluxe Reverb Vibrato PLate Voltage High
Posted: Mon Nov 23, 2015 11:30 pm
Offline
Rock Icon
Rock Icon
User avatar

Joined: Wed Mar 31, 2010 12:48 am
Posts: 26416
Location: Tombstone Territory
BMW2002Ti wrote:
Image


This is the wrong schematic, Steve.

Arjay

_________________
"Here's why reliability is job one: A great sounding amp that breaks down goes from being a favorite piece of gear to a useless piece of crap in less time than it takes to read this sentence." -- BRUCE ZINKY


Top
Profile
Post subject: Re: Deluxe Reverb Vibrato PLate Voltage High
Posted: Mon Nov 23, 2015 11:39 pm
Offline
Rock Star
Rock Star
User avatar

Joined: Sat Jul 03, 2010 2:18 pm
Posts: 6544
Oops! Fixed.

Thanks!


Top
Profile
Post subject: Re: Deluxe Reverb Vibrato PLate Voltage High
Posted: Tue Nov 24, 2015 1:06 am
Offline
Rock Icon
Rock Icon
User avatar

Joined: Tue Jun 29, 2010 1:20 pm
Posts: 9640
Location: Indiana
Good point BMW2002Ti, read voltage from Plate to Cathode, not Plate to ground.

_________________
---> "The amp should be SWITCHED OFF AND UNPLUGGED before you do this!" <---

Por favor, disculpe mi español, no se llega a la práctica con mucha frecuencia.


Top
Profile
Post subject: Re: Deluxe Reverb Vibrato PLate Voltage High
Posted: Tue Nov 24, 2015 2:43 am
Offline
Rock Icon
Rock Icon
User avatar

Joined: Fri Feb 05, 2010 4:31 am
Posts: 14047
Location: Province de Québec, Canada
Retroverbial wrote:
Are you using a 100/100 bias cap?

I've always thought those values were to high compared to the original specs as per the schematic.



Arjay


I always use 100MFD , as I read in Gerald Weber 's books .This work fine and the amp is sometimes more quiet . Less AC ripple on 6V6's grids


Top
Profile
Post subject: Re: Deluxe Reverb Vibrato PLate Voltage High
Posted: Tue Nov 24, 2015 7:08 am
Offline
Rock Icon
Rock Icon
User avatar

Joined: Wed Mar 31, 2010 12:48 am
Posts: 26416
Location: Tombstone Territory
Of course you're free to do as you will.

Leo had his reasons for everything he did and I've learned to never try and second-guess the master.

Arjay

_________________
"Here's why reliability is job one: A great sounding amp that breaks down goes from being a favorite piece of gear to a useless piece of crap in less time than it takes to read this sentence." -- BRUCE ZINKY


Top
Profile
Post subject: Re: Deluxe Reverb Vibrato PLate Voltage High
Posted: Tue Nov 24, 2015 7:59 am
Offline
Rock Icon
Rock Icon
User avatar

Joined: Fri Feb 05, 2010 4:31 am
Posts: 14047
Location: Province de Québec, Canada
Retroverbial wrote:
Of course you're free to do as you will.

Leo had his reasons for everything he did and I've learned to never try and second-guess the master.

Arjay


Leo's bias caps are often (if not always ) under rating bias voltage .

Why ? This is not safe


Top
Profile
Post subject: Re: Deluxe Reverb Vibrato PLate Voltage High
Posted: Tue Nov 24, 2015 8:39 am
Offline
Rock Icon
Rock Icon
User avatar

Joined: Wed Mar 31, 2010 12:48 am
Posts: 26416
Location: Tombstone Territory
So you know more than Leo, eh?

That'll be the day.

:roll:

Arjay

_________________
"Here's why reliability is job one: A great sounding amp that breaks down goes from being a favorite piece of gear to a useless piece of crap in less time than it takes to read this sentence." -- BRUCE ZINKY


Top
Profile
Post subject: Re: Deluxe Reverb Vibrato PLate Voltage High
Posted: Tue Nov 24, 2015 8:48 am
Offline
Rock Icon
Rock Icon
User avatar

Joined: Fri Feb 05, 2010 4:31 am
Posts: 14047
Location: Province de Québec, Canada
Retroverbial wrote:
So you know more than Leo, eh?

That'll be the day.

:roll:

Arjay


Leo was a genius . Maybe no better capacitor is available for him ?

Today I can't see no reason to use a underate voltage capacitor . You see some ?

And wall outlet voltage is higher .


Top
Profile
Post subject: Re: Deluxe Reverb Vibrato PLate Voltage High
Posted: Tue Nov 24, 2015 10:06 am
Offline
Rock Icon
Rock Icon
User avatar

Joined: Wed Mar 31, 2010 12:48 am
Posts: 26416
Location: Tombstone Territory
stratele52 wrote:
Leo was a genius . Maybe no better capacitor is available for him ?


I doubt that. Leo was a large player in the electronic business at that time -- likely he could've spec'd any production component he wished (which he often did).


stratele52 wrote:
Today I can't see no reason to use a underate voltage capacitor . You see some ?


No.

stratele52 wrote:
And wall outlet voltage is higher .


Quite true.

I have no issue with the bias cap's voltage rating -- my concern is excessive filtering (microfarads too high).

Arjay

_________________
"Here's why reliability is job one: A great sounding amp that breaks down goes from being a favorite piece of gear to a useless piece of crap in less time than it takes to read this sentence." -- BRUCE ZINKY


Top
Profile
Post subject: Re: Deluxe Reverb Vibrato PLate Voltage High
Posted: Tue Nov 24, 2015 11:24 am
Offline
Hobbyist
Hobbyist

Joined: Sun Oct 07, 2012 6:48 pm
Posts: 74
Hi Guys

Thanks for all the help. Im really interested in having everything stock on the amp. If for no other reason than to be able to say "this sound (accounting for a different speaker, voltage changes, and age) is as close as reasonably possible to what was intended with this amp"

Bias cap is a 100/100. Schem indicates 25/50. I'll look into that.
Yes re 67, I believe most of the transformers are 66, but I guess it was finished in 67'

BMW, shimmilou: I was measuring voltages at the tube pin to chassis ground?, is that that wrong. Im going to try Pin (plate) to Pin 3 (Cathode) and see what i get.
Should I be measuring at the left and/or right of the 220K resistor? I'll do both anyways and see what the readings are and report back.

I hooked up the foot switch, but I don't know if I had it turned "on" while measuring. I'll try that too.

Re the '820 now 1k" resistor, I don't know why they did that. Im guessing someone just had that 'this is close enough" resistor lying around. I'd also like to put that back to match the schematic.

Answers in 30 min...


Top
Profile
Post subject: Re: Deluxe Reverb Vibrato PLate Voltage High
Posted: Tue Nov 24, 2015 11:52 am
Offline
Rock Icon
Rock Icon
User avatar

Joined: Fri Feb 05, 2010 4:31 am
Posts: 14047
Location: Province de Québec, Canada
Retroverbial wrote:


I have no issue with the bias cap's voltage rating -- my concern is excessive filtering (microfarads too high).

Arjay


Leo did a mistake with underate voltage , why not with MFD ?


Top
Profile
Post subject: Re: Deluxe Reverb Vibrato PLate Voltage High
Posted: Tue Nov 24, 2015 12:24 pm
Offline
Hobbyist
Hobbyist

Joined: Sun Oct 07, 2012 6:48 pm
Posts: 74
Image[/URL]

Here's what I did in order:

Measured from the "Opto coupler" side of the 220K resistor to ground: 414.4 VDC. Toggled with the on off Vibrato switch, and the speed and intensity knobs. No change. 414.4 VDC

Measured from the "choc drop Vibrato Cap" side of the 220k resistor to ground: 406.3 VDC. Toggled with the on off switch on the Vibrato, and the oscillation caused the multi meter to fluctuate a lot (between 180 and 330 VDC)

Measured from Pin 1 (plate), of the Vibrato tube to pin 3 (Cathode): 403 VDC

Measured from pin 6 (plate 2) of the vibrato tube to pin 8 (Cathode 2) 350 VDC

Thoughts?

(I didn't get into the over spec bias cap, or the global feedback resistor, as that seems like a problem for another day)


Top
Profile
Display posts from previous:  Sort by  
Post new topic Reply to topic  [ 21 posts ]  Go to page 1, 2  Next
Go to page 1, 2  Next

All times are UTC - 7 hours

Fender Play Winter Sale 2020

Who is online

Users browsing this forum: No registered users and 2 guests


You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum

Search for:
Jump to: